The invention relates to a two-dimensional array type detecting device, which is a direct conversion type and includes a responsive semiconductor film for directly converting light or radiation to carriers. The invention also relates to a technology for improving a detecting sensitivity and a space resolution.
In recent years, a two-dimensional array type detecting device for detecting light or radiation is used for medical purposes or industrial purposes. As shown in FIG. 8, in a conventional two-dimensional array type detecting device 51, a large number of detecting elements 51a is arranged in order vertically and horizontally according to a two-dimensional array arrangement, and at the same time, elements, not shown, for storing and reading out carriers (electrons or positive holes) produced in the detecting elements 51a by the light or radiation as the object to be detected are disposed to correspond to the two-dimensional array arrangement of the detecting elements 51a, to thereby collect the produced carriers for each element.
In case of the two-dimensional array type detecting device 51 for detecting light, an amorphous silicon (a-Si) film for photodiode is used as a responsive semiconductor film, which produces carriers by responding to the light as the object to be detected or detecting object. Also, in case of the two-dimensional array type detecting device 51 for detecting radiation, such as x-ray, an amorphous selenium (a-Se) film is used as a responsive semiconductor film, which produces carriers by responding to the radiation as the detecting object. Since these detecting devices include the responsive semiconductor films which directly convert light or radiation as the detecting object into the carriers, the devices are called a direct conversion type.
Incidentally, in case of the detecting device for detecting radiation, there can be used a device of an indirect conversion type for indirectly detecting radiation in a two-step structure formed of a phosphor or fluorescent member, such as a CsI (cesium iodide) layer generating light by responding to radiation as the detecting object, and an Si (silicon) layer for photodiode producing carriers by responding to the generated light. In the detecting device of the indirect conversion type, however, since there is a connection loss between the CsI layer and Si layer in addition to the photoelectric transfer loss, the indirect conversion type detecting device is disadvantageous in the detecting sensitivity as compared to the detecting device of the direct conversion type. Also, the detecting device of the indirect conversion type has a disadvantage in the space resolution since there is caused a diffusion of light in the lateral direction of the film.
However, even in the two-dimensional array type detecting device of the direct conversion type, there is a problem that the detecting sensitivity and the space resolution are not high enough. Since the detecting element at a position of generating carriers is not able to collect enough carriers due to leakage and scattering of the carriers, which are produced in the responsive semiconductor film by incidence of light or radiation as the detecting object, the detecting sensitivity and the space resolution are low. If the detecting sensitivity and the space resolution are not sufficient, there is a disadvantage such that, for example, an image quality of a two dimensional image formed based on the detecting signals is deteriorated. Therefore, it has been strongly desired to improve the sensitivity and resolution.
The present invention has been made in view of the foregoing, and an object of the invention is to provide a two-dimensional array type detecting device of a direct conversion type, in which the detecting sensitivity and the space resolution are improved.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To achieve the aforementioned objects, a first aspect of the present invention provides a two-dimensional array type detecting device which comprises a detecting side substrate and a readout side substrate. The detecting side substrate is formed of a common electrode formed on a front surface of a support substrate; a responsive semiconductor film, which is laminated on a front surface side of the common electrode and produces carriers by responding to light or radiation as the detecting object; semiconductor films for junction, which are formed on a front surface of the responsive semiconductor film for the respective sections corresponding to a two-dimensional array layout or arrangement to have hetero-junctions with the responsive semiconductor film; and individual electrodes respectively formed on front surfaces of the semiconductor films for junction. The readout side substrate is formed of a large number of storing elements for storing the produced carriers and a large number of reading elements for reading the carriers, which are respectively formed on a circuit board in a layout corresponding to the two-dimensional array layout in the detecting side substrate. In the detecting device, the detecting side substrate and the readout side substrate are joined such that the respective reading elements are electrically connected to the respective individual electrodes, and light or radiation enters from a side of the support substrate, in which the common electrode is not formed.
Further, a two-dimensional array type detecting device according to a second aspect of the invention comprises a detecting side substrate and a readout side substrate. The detecting side substrate is formed of a common electrode formed on a front surface side of a support substrate; a responsive semiconductor film, which is laminated on a front side of the common electrode and produces carriers by responding to light or radiation as the detecting object; and individual electrodes, which are formed on a front surface of the responsive semiconductor film for the respective sections corresponding to a two-dimensional array layout or arrangement, wherein the individual electrodes have Schottky junctions with the responsive semiconductor film. The readout side substrate is formed of a large number of storing elements for storing the produced carriers and a large number of reading elements for reading the carriers, which are respectively arranged on a circuit board in a layout corresponding to the two-dimensional array layout in the detecting substrate. In the detecting device, the detecting side substrate and the readout side substrate are joined such that the respective reading elements are electrically connected to the respective individual electrodes, and light or radiation enters from a side of the support substrate, in which the common electrode is not formed.
Still further, a two-dimensional array type detecting device according to a third aspect of the invention comprises a detecting side substrate and a readout side substrate. The detecting side substrate is formed of a common electrode formed on a front surface of a support substrate; a responsive semiconductor film with high resistivity laminated on a front side of the common electrode and responds to light or radiation as the detecting object to produce carriers; and individual electrodes, which are formed on a front surface of the responsive semiconductor film for the respective sections corresponding to a two-dimensional array layout. The readout side substrate includes a large number of storing elements for storing the produced carriers and a large number of reading elements for reading the carriers, which are respectively formed on a circuit board in a layout corresponding to the two-dimensional array layout in the detecting side substrate. In the detecting device, the detecting side substrate and the readout side substrate are joined such that the respective reading elements for reading the carriers are electrically connected to the respective individual electrodes, and light or radiation enters from a side of the support substrate, in which the common electrode is not formed.
Also, according to a fourth aspect of the invention, in the aforementioned detecting devices, the detecting side substrate can be provided with a semiconductor film for junction which is interposed between the responsive semiconductor film and the common electrode to have hetero-junctions with the responsive semiconductor film.
Next, operations of the two-dimensional array type detecting devices according to the invention will be explained.
In case of the two-dimensional array type detecting device according to the first aspect of the invention, light or radiation as the detecting object entering from the side of the support substrate, in which the common electrode is not formed, enters into the responsive semiconductor film to produce the carriers (electrons or positive holes) by the direct conversion system, and the produced carriers are collected at the respective individual electrodes, that is, carrier collecting electrodes. Then, in the two-dimensional array type detecting device according to the first aspect of the invention, the front surface of the responsive conductor film is provided with the responsive semiconductor films for junction, which respectively have the hetero-junctions with the responsive semiconductor film and are arranged for the respective sections corresponding to the two-dimensional array layout, so that leak and expansion of the produced carriers can be prevented. Thus, since the carriers are collected at the individual electrodes close to the producing position, the detecting sensitivity and the space resolution can be improved. Namely, a dynamic range is large, and a crosstalk is small.
In case of the two-dimensional array type detecting device according to the second aspect of the invention, light or radiation as the detecting object entering from the side of the support substrate, in which the common electrode is not formed, enters the responsive semiconductor film to produce the carriers (electrons or positive holes) by the direct conversion system, and at the same time, the produced carriers are collected at the respective individual electrodes as the carrier collecting electrodes. Then, in the two-dimensional array type detecting device according to the second aspect of the invention, the front surface of the responsive semiconductor film is provided with the individual electrodes, which respectively have the Schottky junctions with the responsive semiconductor film and arranged thereon for the respective sections corresponding to the two-dimensional array layout, so that leak and expansion of the produced carriers can be prevented. Thus, since the carriers are collected at the individual electrodes close to the producing position, the detecting sensitivity and the space resolution can be improved. Namely, a dynamic range is large, and a crosstalk is small.
In case of the two-dimensional array type detecting device according to the third aspect of the invention, light or radiation as the detecting object entering from the side of the support substrate, in which the common electrode is not formed, enters the responsive semiconductor film with high resistivity to produce the carriers (electrons or positive holes) by the direct conversion system, and at the same time, the produced carriers are collected at the respective individual electrodes as the carrier collecting electrodes. Then, in the two-dimensional array type detecting device according to the third aspect of the invention, on the front surface of the high resistivity responsive semiconductor film, the respective individual electrodes are arranged for the respective sections corresponding to the two-dimensional array layout, so that leak and expansion of the produced carriers can be prevented. Thus, since the carriers are collected at the individual electrodes close to the producing position, the detecting sensitivity and the space resolution can be improved. Namely, a dynamic range is large, and a crosstalk is small.
In addition, in case of the two-dimensional array type detecting devices according to the first, second and third aspects of the invention, since the devices respectively have a structure such that the detecting side substrate for detecting light or radiation and the readout side substrate for storing and reading the produced carriers are manufactured separately and joined, it is prevented that the elements for storing and reading the carriers are exposed to a high heat, which is generated in case of laminating the responsive semiconductor film, and deteriorated.
In case of the two-dimensional array type detecting device according to the fourth aspect of the invention, since the semiconductor film having the hetero-junction with the responsive semiconductor film is interposed between the responsive semiconductor film and the common electrode, the produced carriers are further prevented from leaking and surely collected at the individual electrodes located close to the producing position. Accordingly, the detecting sensitivity and the space resolution are further improved.